From c6d6e9b0f6b4201c77f2cea3964dd122697e3543 Mon Sep 17 00:00:00 2001
From: Jaegeuk Kim <jaegeuk@kernel.org>
Date: Tue, 18 Dec 2018 09:25:37 -0800
Subject: [PATCH] dm: do not allow readahead to limit IO size
Git-commit: c6d6e9b0f6b4201c77f2cea3964dd122697e3543
Patch-mainline: v5.0-rc1
References: git-fixes

Update DM to set the bdi's io_pages.  This fixes reads to be capped at
the device's max request size (even if user's read IO exceeds the
established readahead setting).

(Coly Li: rebased for SUSE 4.12 kernel code base)

Fixes: 9491ae4a ("mm: don't cap request size based on read-ahead setting")
Cc: stable@vger.kernel.org
Reviewed-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Coly Li <colyli@suse.de>
---
 drivers/md/dm-table.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -1854,6 +1854,9 @@ void dm_table_set_restrictions(struct dm
 	 */
 	if (blk_queue_add_random(q) && dm_table_all_devices_attribute(t, device_is_not_random))
 		blk_queue_flag_clear(QUEUE_FLAG_ADD_RANDOM, q);
+
+	/* Allow reads to exceed readahead limits */
+	q->backing_dev_info->io_pages = limits->max_sectors >> (PAGE_SHIFT - 9);
 }
 
 unsigned int dm_table_get_num_targets(struct dm_table *t)